selinux: simplify avc_xperms_audit_required()

By associative and commutative laws, the result of the two 'audited' is
zero. Take the second 'audited' as an example:
  1) audited = requested & avd->auditallow;
  2) audited &= ~requested;
  ==> audited = ~requested & (requested & avd->auditallow);
  ==> audited = (~requested & requested) & avd->auditallow;
  ==> audited = 0 & avd->auditallow;
  ==> audited = 0;

In fact, it is more readable to directly write zero. The value of the
first 'audited' is 0 because AUDIT is not allowed. The second 'audited'
is zero because there is no AUDITALLOW permission.
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

security/selinux/avc.c

@@ -388,7 +388,7 @@ static inline u32 avc_xperms_audit_required(u32 requested,
 		audited = denied & avd->auditdeny;
 		if (audited && xpd) {
 			if (avc_xperms_has_perm(xpd, perm, XPERMS_DONTAUDIT))
-				audited &= ~requested;
+				audited = 0;
 		}
 	} else if (result) {
 		audited = denied = requested;
@@ -396,7 +396,7 @@ static inline u32 avc_xperms_audit_required(u32 requested,
 		audited = requested & avd->auditallow;
 		if (audited && xpd) {
 			if (!avc_xperms_has_perm(xpd, perm, XPERMS_AUDITALLOW))
-				audited &= ~requested;
+				audited = 0;
 		}
 	}